Transcranial Doppler Ultrasound: Physical Principles

This chapter describes the physical principles underlying transcranial Doppler ultrasound. The propagation of ultrasound through tissue is described. The principles of continuous wave Doppler, pulsed wave Doppler, duplex scanning, colour flow imaging and power Doppler imaging are introduced. The use of transcranial Doppler for measuring velocity, flow changes and cerebrovascular resistance, for detecting cerebral emboli and for imaging the cerebral circulation is discussed. Finally, the important issue of ultrasound safety is raised.